In general, wind turbine blades have a pressure surface and a suction surface consisting of laminated composite material joined therebetween and which confer the aerodynamic geometry to the blade. The connection of the pressure and suction surfaces is performed joining their ends and by means of shear webs disposed in the cavity formed by said pressure and suction surfaces. The shear webs stiffen the pressure and suction surfaces to avoid bending of the laminates that form them. The connection between the shear webs and pressure and suction surfaces can be executed in various manners, but the most common is bonding by means of adhesive.
In some cases, the blades are formed by a continuous surface, there not existing a bond defined between the pressure and suction surfaces. Also in these cases, the shear webs stiffen said pressure and suction surfaces and the bond between those and these is usually executed by means of adhesive.
The conventional geometry of the shear webs is I- or C-shaped, although shear webs having L- or T-shaped and even X- or K-shaped geometries are also known. The selection of one type of geometry or another depends on the structural requirements in terms of capacity to transmit the shear stress experienced by the blade due to aerodynamic loads and other solicitations arising during wind turbine operation. This shear stress is transmitted from the shear webs to the pressure and suction surfaces through the bond thereof which, as described previously, is usually an adhesive bond.
The shear webs comprise:                a central zone formed by at least one core and at least two fibre fabric layers disposed on both sides of the central core, and        two bonding zones on both ends of the central zone formed by a continuation of the core fibres.        
Usually, the central zone of the shear web is disposed substantially transversely or obliquely to the blade pressure and suction surfaces. The shear web bonding zones allow adhesive bonding to the blade pressure and suction surfaces and comprise at least one bonding surface substantially parallel to said blade pressure and suction surfaces.
In this manner, each fibre fabric layer of the core forms a shear stress transmission layer such that the shear web usually comprises two layers. As the shear stress must be absorbed by the fibre fabric layers, the distribution of shear stress in the adhesive is not even, generating two shear stress tension peaks corresponding to each of the fibre fabric layers.
This makes it necessary, when using shear webs having a C-shaped geometry, to increase the width of the bond for the purpose of reducing the tension borne by the adhesive. However, this increase in width implies an increased in the use of adhesive material.